Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Biogas is an end product of anaerobic degradation of organic substances and has limited use in power generation mainly due to the presence of hydrogen sulfide (H2S). Currently, most of the techniques employed in the removal of H2S from biogas have a chemical base, with high material costs and generating secondary pollutants. The biological processes for the removal of H2S have become an effective and economical alternative to traditional gas treatment systems based on physicochemical techniques. Therefore, the aim of this work was to investigate the performance of a bench scale biofilter for the removal of H2S present in synthetic biogas. In addition, the concentrations of CO2 and CH4 in the effluent biogas were evaluated. The inoculum used in the experiment was composed of Acidithiobacillus thiooxidans fixed on a packing of wood chips. The synthetic biogas was supplied to the system with a composition of 60% CH4, 39 % CO2 and 1 % H2S. The determination of the concentration of hydrogen sulfide was performed by voltammetry and the concentrations of CH4 and CO2 by gas chromatography. The biofilter operated continuously for 37 days with an average removal efficiency of H2S of 75 ± 13 % and maximum of 97%. The elimination capacity of the system reached an average of 130 ± 23 g.m-3.h-1 and a maximum of 169 g.m3.h-1. The biofiltration system showed an average reduction of only 6 % in the CH4 content of the biogas. Thus, besides efficiently being used for the removal of H2S, the system was able to maintain the biogas energy value. / O biogás é um produto final da degradação anaeróbica de substâncias orgânicas e tem seu uso limitado na geração de energia devido, principalmente, à presença do sulfeto de hidrogênio (H2S). Atualmente, a maior parte das técnicas empregadas na remoção de H2S do biogás tem base química, possuindo altos custos materiais e gerando poluentes secundários. Os processos de remoção biológica de H2S têm se tornado uma alternativa eficaz e econômica para os sistemas tradicionais de tratamento de gás baseados em técnicas físico-químicas. Dessa forma, objetivou-se com este trabalho investigar o desempenho de um biofiltro em escala laboratorial na remoção do H2S presente em biogás sintético. Além disso, avaliaram-se as concentrações de CH4 e CO2 no biogás efluente. O inóculo utilizado no experimento foi composto de Acidithiobacillus thiooxidans fixado em um meio suporte de cavacos de madeira. O biogás sintético fornecido ao sistema possuiu composição de 60% de CH4, 39% de CO2 e 1% de H2S. A determinação da concentração de sulfeto de hidrogênio foi realizada através de voltametria e as concentrações de CH4 e CO2 por cromatografia gasosa. O biofiltro operou continuamente durante 37 dias, apresentando uma eficiência média na remoção de H2S de 75 ± 13% e máxima de 97%. A capacidade de eliminação do sistema atingiu um valor médio de 130±23 g.m-3.h-1 e máximo de 169 g.m-3.h-1. O sistema de biofiltração apresentou uma redução média de apenas 6% no teor de CH4 do biogás. Sendo assim, além de poder ser eficientemente utilizado para a eliminação do H2S, o sistema foi capaz de manter o valor energético do biogás.

Made available in DSpace on 2014-06-11T19:29:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-01Bitstream added on 2014-06-13T20:59:06Z : No. of bitstreams: 1 solcia_rb_me_araiq.pdf: 1432643 bytes, checksum: 92164fbf9e408534eafc69bd3af54fbe (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho foram realizados ensaios para o estudo da viabilidade da conversão de lavadores químicos (tecnologia química muito utilizada para a remoção de H2S) em biofiltros percoladores para a remoção de H2S. Foi investigado o efeito inibitório da concentração de sulfato no meio de recirculação de nutrientes, o efeito do pH, da vazão de recirculação de nutrientes, da concentração de alimentação de H2S na corrente gasosa e do tempo de residência na eficiência de remoção de H2S em dois biofiltros percoladores, um recheado com espuma de poro aberto de poliuretano e o outro com anéis de Pall de polipropileno. Durante a etapa de imobilização dos micro-organismos foi observado, experimentalmente, que o anel de Pall de polipropileno não é um bom suporte para a imobilização de Thiobacillus denitrificans e, portanto, no caso da conversão de um lavador químico constituído por um leito de recheio de anéis de Pall em um biofiltro percolador, seria apropriada a substituição deste suporte por espuma de poro aberto de poliuretano, por exemplo, que demonstrou ser um bom suporte para a formação do biofilme. Durante o estudo do efeito do pH observou-se que o aumento de pH aumenta a porcentagem de remoção de H2S, sendo que nas condições utilizadas, o intervalo de pH ótimo ficou entre 7,6 – 8,5. O efeito inibitório da concentração de sulfato foi observado a partir de 16,5 g L-1 no biofiltro de espuma de poro aberto de poliuretano e de 13,0 g L-1 no biofiltro de anéis de Pall de polipropileno. Os efeitos da vazão de recirculação de nutrientes e do tempo de residência do gás foram mais evidentes no biofitro de anéis de Pall comparado a espuma de poro aberto, devido, provavelmente, às características do suporte. No biofiltro de espuma de poro aberto, a diminuição do tempo de residência afetou a... / In this work experiments were carried out in order to study the viability of conversion of chemical scrubbers (current technology) to biotrickling filter for removing H2S. Many parameters were investigated, such as, the inhibitory effect of sulfate concentration in the nutrient recirculation, the effect of the pH, the flow rate of recirculating nutrient, the inlet H2S concentration and the gas stream residence time in the H2S removal capacity in two biotrickling filter. One of them was packaged with open pore polyurethane foam and other with polypropylene Pall rings. During and after the immobilization stage it was observed, experimentally, that polypropylene Pall rings is not a good support for immobilizing Thiobacillus denitrificans. Thus, in the case of a chemical packaged scrubber conversion using such support in a biotrickling filter, it would be appropriate to replace it by open pore polyurethane foam, for instance, which demonstrated to be a better support to the biofilm to establish. It was shown that increasing the pH an increase in the H2S removal was detected. In this experimental work conditions, the optimum pH range was from 7.6 to 8.5. The inhibitory effect of the sulfate concentration was observed from 16.5 g L-1 in the open pore polyurethane foam biofilter and 13.0 g L-1 in the polypropylene Pall rings biofilter. The effects of the flow rate of the recirculating nutrient and the gas residence time were more evident in the Pall ring biofilter when compared with the open pore foam, probably due to the support characteristics. In the open pore foam biofilter, decreasing the residence time the H2S removal percentage was affected only for less than 9 s, whereas in the Pall rings biofilter, before 33 s. In both biofilters as lower the residence time, lower the H2S removal percentage. In the open pore polyurethane foam... (Complete abstract click electronic access below)

O sulfeto de hidrogênio é um gás que pode causar os mais diversos danos se lançado ao meio ambiente devido, principalmente, à sua elevada toxicidade, corrosividade, odores indesejáveis e alta demanda de oxigênio. Atualmente existem diferentes processos físico-químicos estabelecidos para o tratamento desse composto, entretanto são consideradas técnicas onerosas do ponto de vista econômico e ambiental. Os processos biológicos constituem-se como uma alternativa bastante interessante quando comparados aos processos físico-químicos, sendo que a biofiltração é o processo mais amplamente utilizado. Neste trabalho, foram avaliados três tipos diferentes de materiais suporte, sendo um sintético - espuma de poliuretano - e dois orgânicos - fibra de côco e bagaço de cana -, para a biofiltração de uma mistura gasosa contendo \'H IND.2\'S\'. Como inóculo, optou-se pela utilização de cultura mista originária de duas fontes: a) unidade de biofiltro aerado submerso pertencente ao Serviço Autônomo de Água e Esgoto da Cidade de São Carlos, b) unidade de lodos ativados pertencente a São Carlos S/A - Indústria de Papel e Celulose. A adaptação do inóculo foi realizada em meio nutriente específico. Foi observado um período de partida de somente 2 dias nos três sistemas. Com o intuito de avaliar o impacto do aumento progressivo das taxas de carregamento mássico no desempenho dos três biofiltros, os mesmos foram submetidos a taxas de 19, 32, 54 e 70 g/m³.h (concentrações afluentes médias de 184, 328, 526 e 644 ppm para tempo de retenção do gás de, aproximadamente, 50 segundos). As eficiências remoção média em todos os sistemas mantiveram-se sempre acima dos 99,3%. A capacidade eliminação máxima alcançada pelos biofiltros oscilou entre 74 e 80 g/m³.h. As perdas de carga verificadas no ensaio hidrodinâmico foram baixas, variando entre 0,59.\'10 POT.-2\' a 0,68 \'10 POT.-2\' mca, para a velocidade superficial utilizada durante o estudo. O modelo matemático empregado na previsão do desempenho dos sistemas ajustou-se bem aos dados experimentais. Portanto, pode-se concluir que os materiais suportes testados são adequados para a biofiltração de sulfeto de hidrogênio. / Hydrogen sulfide is a gas which has high restrictions regarding to its disposal in the environment, mainly, because of its high toxicity, malodors, high oxygen demand, etc. Currently, there are many different physical-chemical processes established in order to treat this compound, nevertheless they are considered expensive techniques by the point of economical and environmental views. Biological processes are very interesting alternatives when they are compared to the physical-chemical ones, and biofiltration is the most used process. In this work, three different materials as support media were evaluated, - a synthetic one - represented by the polyurethane foam, - two organic ones - represented by coconut fiber and sugar bagasse -, for a biofiltration of a gaseous mixture containing \'H IND.2\'S\'. Microorganisms were obtained from two sources: a) submerged aerated biofilter unit, b) activated sludge unit. Inoculum\'s adaptation was realized in specific nutrient media. It was observed a 2 days start-up period in the three systems. In order to evaluate some impact caused by the progressive increasing of mass loading rate on the biofilters performance, were applied rates of 19, 32, 54 e 70 g/m³.h (average influent concentrations of 184, 328, 526 e 644 ppm to the empty bed retention time of, approximately, 50 seconds). Average removal efficiencies in the systems were always above 99,3%. Maximum elimination capacities reached by the biofilters were in the range of 74 e 80 g/m³.h. Loss pressure verified by the hands of hydrodynamic essays varied between 0,59.\'10 POT.-2\' a 0,68.\'10 POT.-2\' mca, to a superficial velocity utilized during the work. Mathematical model used to predict the performance of the systems fitted reasonably the experimental data. Then, it can be concluded that the three packing materials are appropriated for the hydrogen sulfide biofiltration.

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An engineered biological filtration (biofiltration) process treating a nutrient-enriched, low-alkalinity, organic-laden surface water downstream of conventional coagulation-clarification and upstream of an ultrafiltration (UF) membrane process was assessed for its treatment effectiveness. The impact of biofiltration pretreatment on UF membrane performance was evaluated holistically by investigating the native source water chemistry and extending the analysis into the drinking water distribution system. The biofiltration process was also compared in treatment performance to two alternative pretreatment technologies, including magnetic ion exchange (MIEX®) and granular activated carbon (GAC) adsorption. The MIEX®, GAC adsorption, and biologically active carbon (BAC) filtration pretreatments were integrated with conventional pretreatment then compared at the pilot-scale. Comparisons were based on collecting data regarding operational requirements, dissolved organic carbon (DOC) reduction, regulated disinfection byproduct (DBP) formation, and improvement on the downstream UF membrane operating performance. UF performance, as measured by the temperature corrected specific flux or mass transfer coefficient (MTC), was determined by calculating the percent MTC improvement relative to the existing conventional-UF process that served as the control. The pretreatment alternatives were further evaluated based on cost and non-cost considerations. Compared to the MIEX® and GAC pretreatment alternatives, which achieved effective DOC removal (40 and 40 percent, respectively) and MTC improvement (14 and 30 percent, respectively), the BAC pretreatment achieved the lowest overall DOC removal (5 percent) and MTC improvement (4.5 percent). While MIEX® relies on anion exchange and GAC relies on adsorption to target DOC removal, biofiltration uses microorganisms attached on the filter media to remove biodegradable DOC. Two mathematical models that establish an empirical relationship between the MTC improvement and the dimensionless alkalinity to substrate (ALK/DOC) ratio were developed. By combining the biofiltration results from the present research with findings of previous studies, an empirical relationship between the MTC improvement versus the ALK/DOC ratio was modeled using non-linear regression in Minitab®. For surface water sources, UF MTC improvement can be simulated as a quadratic or Gaussian distribution function of the gram C/gram C dimensionless ALK/DOC ratio. According to the newly developed empirical models, biofiltration performance is optimized when the alkalinity to substrate ratio is between 10 and 14. For the first time a model has thus been developed that allows for a predictive means to optimize the operation of biofiltration as a pretreatment prior to UF membrane processes treating surface water.

Au Québec, l'enfouissement est la technique la plus répandue pour l'élimination des matières résiduelles. Bien qu'elle soit simple et économique, elle entraîne différentes problématiques, dont la production de lixiviats, des liquides très chargés en contaminants, et de gaz d'enfouissement contribuant à l'émission de gaz à effet de serre. Chez Investissement Québec - CRIQ (IQ-CRIQ), la biofiltration méthanotrophe a été étudiée dans les dernières années pour le traitement combiné de ces deux sources de polluants. Si cette technologie a montré une bonne capacité à traiter le méthane (CH₄) présent dans les gaz d'enfouissement, tout en assimilant de l'azote des lixiviats, la capacité du système biologique à résister aux fluctuations saisonnières de température peut être questionnée. L'objectif principal est donc de vérifier si le caractère exothermique de la réaction d'oxydation du CH₄ par les bactéries méthanotrophes permet de maintenir l'activité biologique au sein du biofiltre et donc la capacité épuratoire du CH₄ et de l'azote nitrate (NO₃-) des lixiviats en période hivernale. Pour ce faire, un montage expérimental comprenant quatre biofiltres avec un garnissage organique a été alimenté avec des lixiviats prétraités provenant d'un site d'enfouissement et un mélange synthétique de gaz composé de gaz naturel et d'air. Des isolants en uréthane et une chambre réfrigérée ont été utilisés afin de reproduire les conditions hivernales sur le terrain d'un biofiltre enfoui, soit une température avoisinant les 4 °C. En ce sens, la température d'alimentation liquide a aussi été diminuée à 4 °C pour deux des quatre biofiltres. L'effet d'une charge en CH₄ plus importante sur le traitement a aussi été exploré. Durant les expérimentations qui se sont étendues sur environ 300 jours, les gaz (CH₄, CO₂, N₂O entre autres) et les liquides (NO₃-, NO₂-, NH₄+, pH entre autres) ont été analysés deux à trois fois par semaine et la température interne des réacteurs a été suivie en continu à l'aide de capteurs. Les expérimentations ont permis de montrer que le maintien du traitement était possible même avec une baisse de la température du liquide d'alimentation : une capacité d'élimination de 98 à 112 gCH₄/m³/j et de 2,6 à 3,2 gN-NO₃-/m³/j a été observée pour le biofiltre à température ambiante (environ 21 °C) alimenté avec un lixiviat à 4 °C alors qu'elle a été de 113 gCH₄/m³/j et de 4,4 gN-NO₃-/m³/j pour le biofiltre témoin (température ambiante et d'alimentation liquide à environ 21 °C). Cependant, le biofiltre alimenté avec des lixiviats à 4 °C et placé dans un environnement avec une température ambiante à 4 °C a vu ses capacités à traiter le CH₄ et le NO₃- devenir nulles lors du changement drastique de température. Finalement, le biofiltre alimenté avec une concentration plus élevée en CH₄ n'a pas été en mesure de traiter davantage de contaminants, ce qui laisse croire qu'il pourrait y avoir un débalancement entre le CH₄, les NO₃- et les autres nutriments essentiels ou encore la présence d'inhibiteurs au sein du biofiltre. Une difficulté des gaz à pénétrer le biofilm a aussi pu limiter la capacité d'oxydation et donc l'enlèvement des NO₃-. Bien que des incertitudes persistent, les résultats obtenus montrent bien un potentiel de maintien des capacités épuratoires par les méthanotrophes en période froide d'opération.

En concentration excessive, le phosphore rejeté à l'environnement favorise la croissance anormalement rapide de la flore aquatique. Des efforts doivent donc être faits pour développer des traitements qui permettront d'abaisser la concentration des rejets à des valeurs pouvant être aussi basses que 0,3 mgPtot/L. En ce sens, des travaux de recherche ont été réalisés. La méthodologie utilisée est basée sur l'utilisation d'un média filtrant constitué de broyure de bois activée imprégnée d'hydroxyde de fer à sa surface. Des essais en colonne ont été réalisés à partir de ce média filtrant. Opérées en immersion durant plus de 250 jours, des colonnes ont été alimentées avec une eau synthétique dopée en phosphore. Par ces essais, il a été mis en évidence que les colonnes opérées en milieu anaérobie sont plus efficaces que les colonnes opérées en aérobie. L'absence d'oxygène entraine une chute progressive du potentiel d'oxydoréduction. Lorsqu'il atteint des valeurs de l'ordre de -100mV, le fer en surface de la broyure se réduit et passe de la forme Fe³⁺ à la forme Fe²⁺. La forme Fe²⁺ étant plus soluble que la forme Fe³⁺, il y a donc une augmentation de la concentration en fer dissout. Appelé dissolution réductive, ce phénomène lent permet la complexation du fer solubilisé avec les ions phosphates en solution. C'est la combinaison de l'adsorption et de la complexation du fer qui permet d'obtenir un média performant. Sur une période de 291 jours, la colonne opérée en anaérobie a permis de maintenir à 85% l'enlèvement du phosphore. Puisque le phénomène de dissolution réductive entraine des relargages de fer et de phosphate ferrique à la sortie de la colonne, le contrôle de ces relargages par l'ajout d'une zone aérobie permet une hausse de la performance globale d'enlèvement du phosphore pour un % d'enlèvement global de 95%.

Le surplus de production de lisier de porc dans certaines régions a mené au développement de technologies permettant de prendre en charge celui-ci, afin de réduire les risques de contamination pour l'environnement. La biofiltration à support organique, constitue une alternative au transport du lisier en traitant in situ ce polluant. Le désir d'optimiser l'enlèvement de l'azote par ce procédé et le besoin d'acquérir de meilleures connaissances au niveau des transformations de ce composant dans le système ont conduit à l'élaboration d'un projet d'envergure visant à mieux comprendre le comportement de l'azote. Ce projet de doctorat s'inscrit donc dans cette mission et avait pour objectifs principaux de développer des outils analytiques permettant de caractériser la biomasse nitrifiante et dénitrifiante présente sur le support du procédé et d'utiliser ces outils pour suivre la colonisation de biofiltres pilotes. La respirométrie azotée de type LSS et le blocage à l'acétylène ont donc été adaptés afin d'évaluer respectivement l'activité nitrifiante et dénitrifiante potentielle d'échantillons du milieu filtrant, tandis que le PCR en temps réel a été utilisé pour quantifier les microorganismes oxydant l'ammoniaque (AOB), Nitrobacter, Nitrospira, les bactéries dénitrifiantes possédant le gène nirS ainsi que les bactéries totales. Trois biofiltres pilotes ont été montés, alimentés avec du lisier de porc ayant des ratios DBOsrNTK différents (3, 6 et 9) et suivis durant 180 jours. Ceux-ci étaient constitués de milieu filtrant organique surmonté d'une couche grossière, principalement composée de pouzzolane. Un échantillonnage régulier des affluents et des effiuents gazeux et liquides des biofiltres, ainsi qu'à différentes hauteurs dans le procédé, ont permis d'observer le profil de la concentration des formes azotées dans les trois biofiltres et de déterminer, par bilan de masse, l'activité observée des couches de milieu filtrant. De plus, un échantillonnage du support a permis de caractériser la biomasse de l'azote dans chaque couche en évaluant son activité potentielle et en la quantifiant par PCR en temps réel. La présence de bactéries nitrifiantes, mise en évidence par leur activité potentielle, a pu être notée dès le début de la période de suivi, mais la nitrification n'a pu être observée qu'aux environs du 40e jour d'opération. Leur activité potentielle a augmenté graduellement jusqu'à la fin des essais. La dénitrification était présente durant toute la durée du suivi et semblait suivre un cycle de croissance-décroissance, particulièrement à partir du jour 80. Pour les trois conditions d'opération, le potentiel à nitrifier et à dénitrifier s'est retrouvé majoritairement en surface du procédé, dans les couches grossières des biofiltres, très peu de biomasse ayant colonisé le milieu filtrant organique. De plus, le potentiel à transformer l'azote, que ce soit par la nitrification ou la dénitrification, était toujours plus élevé que ce qui pouvait être observé dans le procédé. Ceci suggère qu'il serait possible d'optimiser l'enlèvement de l'azote en favorisant l'un ou l'autre des métabolismes. Il existe un lien très fort entre la nitrification et la dénitrification, particulièrement dans les couches grossières des biofiltres. Également, de très fortes concentrations de bactéries dénitrifiantes possédant le gène nirS et de bactéries nitrifiantes ont été retrouvées dans les échantillons environnementaux de milieu filtrant provenant des biofiltres, proposant que ceux-ci croissent à proximité les uns des autres. Ces deux observations appuient fortement l'hypothèse d'une nitrification et dénitrification simultanée (NDS) à l'intérieur du procédé. La quantification réalisée a permis de constater qu'on retrouve une plus forte concentration de Nitrobacter par rapport à Nitrospira, contredisant plusieurs études récentes ayant démontré la tendance inverse dans les procédés à biomasse en suspension traitant des effluents municipaux. De plus, il a été possible de démontrer que les bactéries dénitrifiantes possédant le gène nirS contribuent fortement à l'activité dénitrifiante potentielle mesurée à l'aide du blocage à l'acétylène. Par contre, la respirométrie azotée ne semble pas être en mesure de bien décrire l'évolution de chaque groupe impliqué dans la nitrification, mais de le faire plutôt pour le comportement global de cette biomasse. Finalement, très peu de différences ont pu être observées au niveau des performances et de la colonisation des biofiltres alimentés à des ratios de 3 et 6. Par contre, celui alimenté à un ratio de 9 a montré des divergences majeures comparées aux deux autres. En effet, une hausse importante du pH , une perte d'efficacité au niveau de l'enlèvement de la DCO et de l'alcalinité et une forte coloration ont pu être observées après seulement quelques semaines d'opération. De plus, la biomasse nitrifiante, quoique démontrant un potentiel important, semble avoir eu de la difficulté à s'établir dans le procédé à ce ratio. Les résultats obtenus pourront être utilisés pour mieux cibler les changements à apporter pour l'optimisation de l'enlèvement de l'azote. Également, ceux-ci permettent de mieux comprendre de quelle façon la biomasse impliquée dans les transformations de l'azote colonise le biofîltre ainsi que son comportement à l'intérieur du procédé. / Producing pig manure in excess in some regions has brought new technological advances allowing its treatment, in order to reduce contamination risks associated with its presence in natural ecosystems. BIOSOR™-Manure, an organic biofilter, is an interesting alternative to its transportation as it treats pig manure on site. The necessity to optimize nitrogen removal by this process and to get a better knowledge about its transformation inside the System has led to a scientific project aiming at those needs. This PhD project constituted a part of it and had as objectives to develop analytical methods to characterize nitrifying and denitrifying biomasses present on the biofilter media and to utilize them to monitor pilot biofilters colonization. LSS nitrogen respirometry and acetylene blockage technique were adapted to respectively evaluate potential nitrifying and denitrifying activities of media samples, while real-time PCR was realized to quantify ammonia oxidizing bacteria (AOB), Nitrobacter, Nitrospira, denitrifying bacteria containing nirS gene and total bacteria. Three pilot biofilters were installed, fed with pig manure having different BODs:TKN ratios (3, 6 and 9) and monitored during 180 days. They were all the same, being made with an organic layer surmounted by a coarse layer (pozzolana). Regular sampling of liquid and gaseous influents and effluents and at different depths allowed the observation of each section for its concentration of gaseous and aqueous nitrogen. Those data were used to calculate a nitrogen mass balance in order to determine the observed activity in each layer. Moreover, regular media sampling was made to characterize the nitrogen biomass by evaluating its potential activity and its quantity. Nitrifiers' presence, followed by potential nitrifying activity, was noted at the beginning of the monitoring period, but nitrification was only observed after approximately 40 days of operation. Its potential activity gradually increased until the end of the project. Denitrification was present ail along and seemed to follow a growth-decay cycle, particularly after 80 days. For the three operational conditions, almost ail of the potential nitrifying and denitrifying activities could be observed near the surface of the process, in the coarse layers, very little biomass being able to colonize the organic media. Moreover, nitrogen removal potential was always higher as that could be seen in the process, both for nitrification and denitrification. It suggests that it is possible to optimize nitrogen removal by promoting one or another of the metabolism. There was a strong correlation between nitrification and denitrification, particularly in the coarse layers. Also, we found high concentrations of nirS denitrifiers and nitrifying bacteria in the same environmental samples, proposing that those grow near each other. Both these observations support the hypothesis that there is simultaneous nitrification and denitrification (SND) inside this process. Quantification showed higher concentration of Nitrobacter compared to Nitrospira, contradicting previous recent studies that demonstrated the reverse trend in suspended biomass processes treating urban wastewaters. Also, it has been possible to fmd that nirS denitrifiers strongly contributed to the potential denitrifying activity, evaluated with the acetylene blockage technique. However, nitrogen respirometry did not seem to describe well each nitrifying group evolution, but only allowed to understand the global behavior of this biomass. Finally, very few differences could be observed between biofilters fed with 3 and 6 BODs:TKN ratios, both for performances and colonization. However, the biofilter fed with a higher ratio (9) showed important dissimilarities compared to the others. In fact, an important increased of pH, a decrease of efficiency for COD and alkalinity removal and a strong brown coloration could be observed only a few weeks after the start-up. Moreover, nitrifying biomass, while showing a good potential activity, seemed to have difficulties to colonize the System. Results could be used, in order to optimize nitrogen removal, to change operational conditions a better way, know knowing what the biomass is capable of and where it can be found in the process. Also, these data allow a better understanding of how the nitrifying and denitrifying biomass colonizes the biofilters and of its behavior inside the System.

In order to evaluate the effect of seaweeds in bio-filtration for removing nitrogen from marine aquaculture and in bioenergy production, Ulva sp. was used in this study. Experiments were triplicated and run in 3-day incubation at salinities with 30 psu, 10 psu and 5 psu in different initial ammonium nitrogen concentrations from 100 μM to 10,000 μM, equivalently to marine aquaculture conditions. The highest concentrations of ammonium removed were about 690 μmol (12.42 mg) NH4+ at 30 psu, 410 μmol (7.38 mg) NH4+ at 10 psu and 350 μmol NH4+(6.3 mg NH4+) at 5 psu in three days of incubation, while highest growth rates of Ulva sp. were 49% and 150% per day at 500 μM of initial ammonium concentration, similarly to the growth rate reported in microalgae. Moreover, after these experiments, biomass of Ulva sp. has been tested for bioenergy producing goals, because the carbohydrate concentration of this alga was very high, reaching 60-70% of DW. Thus, Ulva sp. can be cultured to remove nitrogen concentration in eutrophication conditions at aquaculture systems in combination with the purpose of bioenergy production after harvesting. / Để đánh giá hiệu quả của tảo biển trong việc lọc sinh học loại bỏ hợp chất ni tơ từ việc nuôi trồng thủy sản và trong việc sản xuất năng lượng sinh học, Ulva sp. đã được sử dụng trong nghiên cứu này. Các thí nghiệm được lặp lại 3 lần và chạy trong 3 ngày trong tủ ổn nhiệt tại các điều kiện độ mặn 30psu, 10psu, 5psu ở các nồng độ NH4+-N từ 100μM đến 10.000μM, tương đương với điều kiện nuôi trồng thủy sản nước mặn. Nồng độ cao nhất của NH4+-N được loại bỏ khoảng 690 μmol NH4+(12,42mg NH4 +) tại 30psu, 410μmol NH4+(7,38mg NH4+) tại 10psu và 350 μmol NH4+(6.3mg NH4+) tại 5psu, trong đó tỉ lệ sinh trưởng của Ulva sp. là rất cao, sinh trưởng từ 49 đến 150% mỗi ngày tại nồng độ ammonium ban đầu 500 μM tương đương với sinh trưởng của vi tảo. Hơn nữa, sau các thí nghiệm trên, sinh khối của Ulva sp. được thử nghiệm sản xuất năng lượng sinh học vì hàm lượng carbohydrate trong tảo rất cao, chiếm khoảng 60-70% trọng lượng khô của tảo. Như vậy, Ulva sp. có thể được nuôi trồng để loại bỏ hợp chất ni tơ trong điều kiện phú dưỡng của các hệ thống nuôi trồng thủy sản, kết hợp với mục tiêu sản xuất năng lượng sinh học sau thu hoạch.